In industries like automotive, aerospace, and marine appliances, surface coatings play a vital role in not only protecting components in terms of anticorrosion, but also in enhancing aesthetic appeal. Deterioration of plastic, metal, and glass surfaces is of primary main concern in these applications. Various external factors like solid (dust particles, burnt hydrocarbon, etc.) and liquid (moisture, chemicals, muddy water, etc.) are affecting the substrates in day to day life. This problem is more severe for metals, typically when water droplets dry on the surface, water mark, or spots are left behind due to the deposit of minerals, which when are further in contact with water and oxygen can lead to corrosion cell formation. In a similar fashion plastic and glass surfaces also facing the problem of stains or water marks after evaporating the water, which further affects the aesthetic of the coated plastic components and see-through vision of wind shield glasses. However this solid, liquid, or gaseous adsorption, or wettability phenomenon is unavoidable for any surface, and requires extra physical work and time to clean those substrates. An understanding of the wettability of various materials is required, based on the physical and chemical heterogeneity of the materials.
There are many products on the market that are used to repel water from surfaces, where the expulsion of water is desired. However these available water repellent coatings have certain disadvantages as discussed in the foregoing session.
U.S. Patent Publication 2011/0206925 (Kissel et al.) teaches a polymer aero-gel based super hydrophobic coating which can be achieved with a three step procedure. As per this invention annealing as a surface treatment by heating at 150° C. for 3 hours is required to cure the coating on the substrate, and a contact angle may be achieved only up to 140°.
U.S. Patent Publication 2011/0177252 (Kanagasbapathy et al.) discloses a method of preparation of super hydrophobic coating, which comprises hydrophobic nano-particles of silsesquioxanes containing adhesion promoter group and a low surface energy group. The coating is applied on already painted/wax applied metal/wood/glass/ceramic surface. In the method disclosed, the reaction is not with a substrate, and was found inferior with regard to long term durability.
U.S. Patent Publication 2011/0159299 (Linforf et. al.) discloses a hydrophobic coating application wherein the application steps include surface treatment with plasma. Linforf et al. further discloses a water contact angle up to 120°. However, the disclosed hydrophobic layer of the composition requires the plasma surface treatment.
U.S. Patent Publication 2009/0064894 (Baumaret et al.) teaches a water based hydrophobic self-cleaning coating composition which is opaque in nature. However, the coating composition of this invention is not durable.
U.S. Patent Publication 2007/0141306 (Kasai et al.) discloses a process for preparing a super hydrophobic coating wherein the sliding angle/rolling angle of 25° or less for a deposited 0.02 mL water droplet, after immersion in water for a period of 1 hour is disclosed. The drawback of this disclosed coating is the peel off effect after immersion in water for a period of 1 hour.
Therefore, there is a need for an improved hydrophobic coating that alleviates all the problems of the prior art as mentioned above.